sub imap {
    my ($transform, $it) = @_;
    return Iterator {
        my $next = NEXTVAL($it);
        return unless defined $next;
        return $transform->($next);
    }
}

##</code><code>##

#!/usr/bin/env perl
use 5.010;
use strict;
use warnings;

sub foo(&@) {
    my $coderef = shift;
    my @params = @_;
    my @ret;

    while(@params) {
        push @ret, $coderef->($_);
    }
    return @ret;
}

my @a = ( "1", "2", "3", "4", );
my @b = foo { $_ ** 2 } @a;

##</code><code>##

my @b = foo { $_ = shift; $_ ** 2 } @a;
my @b = foo { my $var = shift; $var ** 2 } @a;

##</code><code>##

#!/usr/bin/env perl
use 5.010;
use strict;
use warnings;

sub foo(&@) {
    my $coderef = shift;
    my @params = @_;
    my @ret;

    for(@params) {
        push @ret, $coderef->();
    }
    return @ret;
}

my @a = ( "1", "2", "3", "4", );
my @b = foo { $_ ** 2 } @a;